论文标题

椭圆形超音速喷气形态操纵使用尖端的裂片

Elliptic supersonic jet morphology manipulation using sharp-tipped lobes

论文作者

Rao, Srisha M. V., Karthick, S. K., Anand, Abhinav

论文摘要

椭圆形喷嘴几何形状对于混合超音速飞机的增强具有吸引力。但是,诸如拍打之类的喷气动力学会产生高强度的音调声音。我们通过使用两个尖端的裂片来实验操纵超音速椭圆形的形态。将裂片放在椭圆喷嘴的次级任一端。设计的马赫数以及椭圆形喷嘴和叶喷嘴的纵横比为2.0和1.65。在几乎完美扩展的条件下,超音速射流耗尽了环境。进行时间分辨的Schlieren成像,纵向和横截面平面激光散射成像,平面粒子图像速度测定法和近场麦克风测量值以评估两个喷嘴的流体行为。在Schlieren和MIE散发图像上进行了动态模式和正确的正交分解(DMD和POD)分析。通过图像处理程序从MIE散落图像中提取混合特性。拍打椭圆机由两种主导的DMD模式组成,而叶喷嘴只有一个主导模式,并且抑制了拍打。麦克风测量显示了相关的降噪。喷射柱在裂片喷嘴中分叉,使较大的表面接触区域具有环境流体和较高的混合速率,在喷嘴出口的近场中。两瓣喷嘴的喷射宽度生长速率约为近场椭圆喷射的两倍,并且潜在的核心长度降低了40 \%。粒子图像速度法(PIV)轮廓证实了结果。

Elliptic nozzle geometry is attractive for mixing enhancement of supersonic jets. However, jet dynamics, such as flapping, gives rise to high-intensity tonal sound. We experimentally manipulate the supersonic elliptic jet morphology by using two sharp-tipped lobes. The lobes are placed on either end of the minor axis in an elliptic nozzle. The design Mach number and the aspect ratio of the elliptic nozzle and the lobed nozzle are 2.0 and 1.65. The supersonic jet is exhausted into ambient at almost perfectly expanded conditions. Time-resolved schlieren imaging, longitudinal and cross-sectional planar laser Mie-scattering imaging, planar Particle Image Velocimetry, and near-field microphone measurements are performed to assess the fluidic behavior of the two nozzles. Dynamic Mode and Proper Orthogonal Decomposition (DMD and POD) analysis are carried out on the schlieren and the Mie-scattering images. Mixing characteristics are extracted from the Mie-scattering images through the image processing routines. The flapping elliptic jet consists of two dominant DMD modes, while the lobed nozzle has only one dominant mode, and the flapping is suppressed. Microphone measurements show the associated noise reduction. The jet column bifurcates in the lobed nozzle enabling a larger surface contact area with the ambient fluid and higher mixing rates in the near-field of the nozzle exit. The jet width growth rate of the two-lobed nozzle is about twice as that of the elliptic jet in the near-field, and there is a 40\% reduction in the potential core length. Particle Image Velocimetry (PIV) contours substantiate the results.

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